Add the macaroni, water, salt and butter into the Instant Pot insert.
Shut, select manual high pressure, set the timer for 4 mins and cook.
Let NPR (Natural Pressure Release) for 8 mins and then do a Quick Release and open.
Quickly stir in the warm milk and cheeses, mix till melted, adjust seasoning, add any toppings or mix-ins and serve.
Evaporated Milk Version
Replace the 1 cup warm milk with 1 cup warm evaporated milk.
Add 4 heaped tbsp pesto at the end.
Add 100g (2/3 cup) ham cut into smaller bits at the end.
Add 160g (1 cup) cooked peas at the end.
You can use a pasta of your choice, but not gluten-free pasta (as it will not hold together).The total cook time does not include the time it takes for the Instant Pot to get to pressure. Plan for additional time.